The pulp science-fiction magazine had been left in his family’s posh Upper East Side apartment by a maid.

Fred Ordway picked it up and knew from that moment what he would grow up to be.

Mr. Ordway, 87, who died July 1 in Huntsville, Ala., devoured science-fiction magazines after that — chronicles of flying saucers, green aliens and Buck Rogers.

His fascination would propel him to the inner circle of leading American aeronautical scientists, working alongside Wernher von Braun at NASA’s Marshall Space Flight Center. Born when ice was still delivered by horse cart, Mr. Ordway joined teams that sent Apollo astronauts to the moon.

And then, having seen his childhood fantasies made real, Mr. Ordway tended to the next generation’s fantasies: He served as technical adviser on Stanley Kubrick’s 1968 classic film, “2001: A Space Odyssey.”

That film’s mesmerizing power owes much to Mr. Ordway.

He was a friend of Arthur Clarke — whose fiction inspired the film — and ensured that what the movie “claimed about this idealized world had some validity to it,” said Benjamin H. Bratton, a visual arts professor at the Arthur C. Clarke Center for Human Imagination at the University of California at San Diego.

Details that might have been glossed over in other movies were painstakingly reproduced frame by frame in Kubrick’s masterpiece — a floating pen, for example, and Velcro slippers worn by space flight attendants to keep them from drifting upward.

Without these “little touches,” the movie risked being dismissed as just a “spacey, hippie-dippie, psychedelic fantasy,” said Sheldon Brown, director of the Clarke Center.

Instead, the film’s transcendence is achieved in part by its juxtaposition of heady themes with minute detail, many of them provided by Mr. Ordway. Lovingly choreographed scenes of an astronaut moving from weightlessness to microgravity help ground the film even as its larger themes ascend to heights of abstraction, Brown said.

Frederick Ira Ordway III was born in New York on April 4, 1927, the only son of a wealthy banking family. The pulp fiction of the 1930s he consumed featured flying saucers, machine wonders and depictions of the Earth that looked like road maps printed on a ball. They offered a mostly optimistic view of the future that would change in the atomic age, said Alison Scott, former bibliographer at Harvard University, to which Mr. Ordway donated his pulp-fiction archive. Mr. Ordway received an engineering degree at Harvard and served briefly in the Air Force Reserve after World War II before joining the burgeoning rocket industry.

Mr. Ordway was always well-dressed and humble in manner, and his strength was in making complex topics clear.

He served as a liaison among scientists and also worked as an educator, speaker and writer. His books included “2001: The Heritage and Legacy of the Space Odyssey” (with Robert Godwin), for anyone interested in space travel.

He interviewed engineers across disciplines for material for “2001.”

“He could talk to anyone about anything,” said his son Frederick Ordway IV, who confirmed his father’s death but did not disclose the cause.

His son recalled the whole family moving to England while his father worked on the film. Every detail of the movie set had to be perfect, his son said, because “they didn’t know where Kubrick was going to point the camera.”

The result: Even images that flash by are elaborately constructed meditations on how future technology might work. The camera whisks over the posted instructions for using a zero-gravity toilet, Brown said — actual instructions, researched to every detail.

The movie, like those early pulp magazines, is optimistic — “light and clean and orderly,” Bratton said, compared with later dystopian science fiction.

Mr. Ordway’s private views of the future, especially of such ecological issues as climate change, departed from that sunny view, his son said.

But his love for space exploration never dimmed. He remained as excited as when he first encountered those fictional flying saucers and felt that “by golly, this stuff is possible,” said longtime friend Tom Crouch, senior curator of aeronautics at the National Air and Space Museum.

Mr. Ordway’s wife of 62 years, Maruja Arenas, died in 2012.

Survivors include two children, Frederick Ordway IV of Huntsville, and Aliette Marisol Lambert of Powhatan, Va.